This invention relates to improvements in cordless, battery operated pens for inputting data and information into a tablet computer. More specifically, the invention relates to a pen having an improved low power oscillator.
Cordless and untethered magnetic pens are known in the prior art, which are used to input data into a tablet computer. One such pen emits a modulated radio frequency (RF) signal that is received and demodulated by electronics with the tablet computer. The detected information is used by the system software to determine the location of the pen with respect to a magnetic grid thereby allowing a user to input data into the computer. The pen includes an oscillator which oscillates at two different frequencies to provide a proximity frequency for detecting when the pen is close to engaging the magnetic grid, and a contact frequency for detecting the location of the pen when the pen is in actual contact with the grid. The pen uses a non-rechargeable battery and it is desirable to limit power consumption as much as possible and thereby prolong battery life. Most of the battery power drain is due to the oscillator (as much as 98%) so that it is highly desirable to provide an efficient low-power oscillator.